The present invention is directed to a temperature curing apparatus and method. While the invention is described with respect to curing ink on a fabric, it is capable of other applications including other types of ink printing, food preparation, plastic forming, and the like.
Many inks require a certain amount of heat in order to cure. In most print shops, products are produced on a continuous basis at ever-increasing speeds. Traditional curing methods have employed heat presses, drawer dryers, and tunnel dryers. However, as the printing machinery capacity has increased, the associated capacity of the curing technology has remained stagnant.
Tunnel dryers, which exist mainly as gas dryers and infrared dryers, either have a series of radiant infrared panels arranged above a continuous belt or one or more gas burners heating air, which is then blown through the belt. Product is placed on a belt at the front of the dryer, and moves at a constant speed through the length of the tunnel. The product is then removed from the back of the dryer, or simply drops off the belt into a catch container. The continuous nature of the dryer dramatically reduces the labor associated with placing items on the curing unit, and then removing them after they are cured, and are inherently scalable, since they can be made arbitrarily long to accommodate arbitrarily fast printing speeds. However, infrared dryers have a major disadvantage in that the final temperature of the product depends on the temperature of elements and the belt speed (the amount of time the product is under the elements). A delicate balance exists between belt speed and element temperature as product continues to absorb energy as long as it is under the elements, and so it never reaches an equilibrium temperature. If the product is in the chamber for too short a time, it never reaches cure temperature. Conversely, if the product is in the chamber for too long a time, it will overshoot its cure temperature and may scorch or dull the ink. Since many factors affect the time required to reach cure temperature (initial product temperature, initial humidity of product, amount of ink deposit on the product, initial temperature of the tunnel, etc.), the product defect rate from an IR dryer is often higher than desired. Gas dryers have a major disadvantage in that the rate of heat transfer from the air to the product decreases as the product approaches the temperature of the air. Thus, gas dryers are inherently slower than similarly-sized infrared dryers. While there are several different technologies currently on the market to cure inks, they all have very significant drawbacks.